Method for determining pump flow rate

ABSTRACT

The present invention relates to a method for determining a flow rate indicator relating to the output flow rate of one or more activated pumps of a pumping station. The pumping station includes a well configured to receive or supply fluid flow. The method includes the step of determining, using a computational device, an operating condition relating to the activated pumps. The activated pumps are temporarily deactivated and a well flow rate relating to the fluid flow is determined, responsive to the determination of the operating condition. The method further includes the step of determining the pump output flow rate indicator using the determined well flow rate. The step of temporarily deactivating the activated pumps involves deactivating the activated pumps for a predetermined period of time and determining the well flow rate over that period of time.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119 AND/OR §120

The present Application for Patent is a continuation application of, andclaims priority to, U.S. patent application Ser. No. 12/366,580,entitled “METHOD FOR DETERMINING PUMP FLOW RATE,” and filed Feb. 5,2009, which claims priority to Australian Patent Application No.:2008900591 entitled “A METHOD FOR DETERMINING PUMP FLOW RATE,” and filedon Feb. 8, 2008 and Australian Patent Application No.: 2008229735entitled “A METHOD FOR DETERMINING PUMP FLOW RATE,” and filed on Oct. 1,2008, each of which is assigned to the assignee hereof, and expresslyincorporated herein by reference.

TECHNICAL FIELD

The present invention generally relates to pumping stations. The presentinvention has particular, although not exclusive application to wastewater pumping stations.

BACKGROUND

The reference to any prior art in this specification is not, and shouldnot be taken as an acknowledgement or any form of suggestion that theprior art forms part of the common general knowledge.

Pumping stations 2 for emptying sewage wells (FIG. 1 a) and fillingwater wells (FIG. 1 b) are known. As shown in FIG. 1 a, waste water andsewage is supplied to the well 4 via an inlet 7 and the pumps 10 areconfigured to empty the well 4. In contrast, FIG. 1 b shows that waterdrains from the water well via outlet 9 and the pumps 10 are insteadconfigured to fill the well 4.

These pumping stations 2 include the well 4 in which liquid 6 islocated, a level sensor 8 for sensing the liquid level in the well 4, apair of pumps 10 a, 10 b for pumping liquid into or out of the well 4 asrequired, and a controller (not shown) in communication with sensor 8and for controlling the operation of the pumps 10 a, 10 b based on thesensed liquid level in the well 4. FIG. 1 shows various leveltrigger-points along the level sensor 8 in the form of liquid sensingelectrodes. The controller independently activates or de-activates thepumps 10 a, 10 b with hysteresis in response to it sensing the liquidlevel via the electrodes.

The controller can display the instantaneous output flow rate of thepumps 10 upon a display which a pumping station supervisor can monitor.The instantaneous flow rate can be sensed using a flow meter, however,such sensors are undesirably expensive. As a cheaper alternative, theflow rate for each pump cycle can instead be estimated.

A known flow rate estimation method is now briefly described withreference to FIG. 1 a. The inflow rate (I) through inlet 7 can bereadily determined, when the pumps 10 are deactivated, as follows:

$\begin{matrix}{I = \frac{\Delta \; V_{well}}{\Delta \; t}} & (1)\end{matrix}$

wherei ΔV_(well) is the change in liquid volume in the well 4 that canbe measured using sensor liquid or 8 and Δt is the change in time.

Upon activation of one or both of the pumps 10, the output flow rate (F)of the pumps 10 can be determined by the following equation:

$\begin{matrix}{F = {\frac{\Delta \; V_{well}}{\Delta \; t} + I}} & (2)\end{matrix}$

where the inflow (I) is measured once immediately prior to theactivation of the pumps 10. However, the inflow (I) may be prone tovariation during a pump activation cycle. Therefore the output flowrates of the pumps can instead be determined by averaging a number ofprior calculations of the flow rate.

When the pumps 10 are continuously activated for a long period of timeduring a pumping cycle, the output flow rate (F) of the pumps 10 caninstead be determined, by averaging a number of prior inflow rates (I)determined when the pumps 10 were deactivated, as follows:

$\begin{matrix}{F = {\frac{\Delta \; V_{well}}{\Delta \; t} + I_{ave}}} & (3)\end{matrix}$

where I_(ave) is the average inflow rate determined by averaging anumber of previous inflow rates (I) determined in accordance with Eq. 1(e.g. ten previous inflow rates).

However, the flow rate (F) determined in accordance with Eq. 3 canbecome inaccurate under certain circumstances including, for example,when the actual inflow rate suddenly changes significantly (e.g. duringa downpour). In this event, the displayed flow rate (F) is reduced andthe pumping station supervisor cannot reliably ascertain whether a pump10 is blocked or the actual inflow rate through inlet 7 has increased,which is clearly undesirable.

It is an object of the present invention to provide a method of moreaccurately determining the output flow rate (F) of the activated pumpsthan the method described above in relation to Eq. 3.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided amethod for determining a flow rate indicator relating to the output flowrate of one or more activated pumps of a pumping station, the pumpingstation including a well to be at least partially emptied by the pumpsand an inlet through which inflow can be supplied into the well, themethod including the steps of: determining, using a computationaldevice, an operating condition relating to the activated pumps;temporarily deactivating the pumps and determining an inflow rateindicator relating to the inflow using the computational device,responsive to the determination of the operating condition; anddetermining, using the computational device, the flow rate indicatorusing the determined inflow rate indicator. The operating condition maybe that the flow rate indicator is less than a predetermined flow ratethreshold. The predetermined flow rate threshold may be calculated as apercentage reduction of a prior flow rate indicator. The operatingcondition may be that the pumps have been activated for a period morethan a predetermined time threshold. The predetermined time thresholdmay be calculated as a percentage increase of a prior duration that thepumps were activated. Prior to the step of temporarily deactivating thepumps, the method may further include the step of determining that thewell level does not exceed a predetermined well level threshold. Thestep of temporarily deactivating the pumps typically involvesdeactivating the pumps for a predetermined period of time anddetermining the inflow rate indicator over that period. The step ofdetermining the flow rate indicator may involve using a determined wellvolume rate indicator. The method may further include the step ofdisplaying any one or more of the determined: inflow rate indicator,flow rate indicator and well volume rate indicator.

According to another aspect of the present invention, there is provideda method for determining a pump flow rate indicator relating to theoutput flow rate of one or more activated pumps of a pumping station,the pumping station including a well configured to receive or supplyfluid flow, the method including the steps of: determining, using acomputational device, an operating condition relating to the activatedpumps; temporarily deactivating the pumps and determining a well flowrate indicator relating to the fluid flow using the computationaldevice, responsive to the determination of the operating condition; anddetermining, using the computational device, the pump flow rateindicator using the determined well flow rate indicator.

According to another aspect of the present invention, there is provideda method for determining a flow rate indicator relating to the outputflow rate of one or more activated pumps of a pumping station, thepumping station including a well to be at least partially filled by thepumps and an outlet through which outflow can exit from the well, themethod including the steps of: determining, using a computationaldevice, an operating condition relating to the activated pumps;temporarily deactivating the pumps and determining an outflow rateindicator relating to the outflow using the computational device,responsive to the determination of the operating condition; anddetermining, using the computational device, the flow rate indicatorusing the determined outflow rate indicator.

According to a further aspect of the present invention, there isprovided the computational device configured to perform any one or moreof the preceding methods. Preferably, the computational device is a pumpcontroller.

According to a further aspect of the present invention, there isprovided a pump controller for determining a pump flow rate indicatorrelating to the output flow rate of one or more activated pumps, thepump controller being configured to: determine an operating conditionrelating to the activated pumps; temporarily deactivate the pumps anddetermine a well flow rate indicator relating to fluid flow of a well,responsive to the determination of the operating condition; anddetermine the pump flow rate indicator using the determined well flowrate indicator.

According to another aspect of the invention there is provided a pumpcontroller for determining a pump flow rate indicator relating to theoutput flow rate of one or more activated pumps, the pump controllerincluding: a processor in communication with ports for connection to oneor more activated pumps; and a memory in communication with theprocessor, the memory containing a software product including: routinesfor determining an operating condition relating to the activated pumps;routines for temporarily deactivating the pumps and determining a wellflow rate indicator relating to fluid flow of a well, responsive to thedetermination of the operating condition; and routines for determiningthe pump flow rate indicator using the determined well flow rateindicator.

According to a further aspect of the present invention, there isprovided a media, such as a magnetic or optical disk or solid statememory, containing computer readable instructions for execution by aprocessor to thereby perform any one or more of the preceding methods.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred features, embodiments and variations of the invention may bediscerned from the following Detailed Description which providessufficient information for those skilled in the art to perform theinvention. The Detailed Description is not to be regarded as limitingthe scope of the preceding Summary of the Invention in any way. TheDetailed Description will make reference to a number of drawings asfollows:

FIG. 1 a is a schematic diagram of a pumping station for emptying asewage well.

FIG. 1 b is a schematic diagram of a pumping station for filling a waterwell.

FIG. 2 is a block diagram showing a pump controller suitable for usewith either pumping station of FIG. 1 a or FIG. 1 b.

FIG. 3 is a flowchart showing a method in accordance with an embodimentof the present invention, the method being suitable for determining apump flow rate for the pumps of the pumping station of FIG. 1 a andperformed by the controller of FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An embodiment of the present invention will now be described withreference to a controller 14 shown in FIG. 2 that is configured tocontrol the pumping station 2 shown in FIG. 1 a.

Referring initially to FIG. 1 a, the pumping station 2 includes a levelsensor 8 for sensing the liquid level in a well 4, and a pair of pumps10 a, 10 b (e.g. three-phase variable speed drive pumps) for pumpingliquid out of the well 4 to at least partially empty the well 4. Wastewater including storm water flows into the well 4 through inlet 7. Thecontroller 14 is suitable for controlling the activation anddeactivation of the pumps 10 based on the sensed liquid level in thewell 4. The activation and deactivation trigger points along the levelsensor 8 for a first pump 10 a and a second pump 10 b are clearly shownin FIG. 1 a. The controller 14 can also determine a well volumeindicator (in the form of a variable or value), relating to the liquidvolume in the well 4, using the liquid level sensor 8. Typically, thelevel sensor 8 includes an array of equidistant electrode sensingstations, and the uppermost triggered station corresponds to the wellliquid level which, in turn, can be correlated to a corresponding liquidvolume in the well 4 (using a look-up table).

Referring to FIG. 2, a user interface 12 is provided to enable thepumping station supervisor to input data to the controller 14 and reviewcontroller data relating to the operation of the pumping station 2 on adisplay. For example, the controller 14 is configured to display a flowrate indicator (F) relating to the output flow rate of the activatedpumps 10 a, 10 b, an inflow rate indicator (I) relating to the inflowthrough inlet 7, and a net well volume rate indicator (i.e. F−1). Theuser interface 12 is fixedly wired to fixed input/output (I/O) ports 16of the controller 14 which, in turn, are interfaced using suitablecircuitry to a microprocessor 19 that executes a software product 20.

The level sensor 8 and pumps 10 are wired to variable I/O ports 18 ofthe controller 14 which, in turn, are interfaced using suitablecircuitry to the microprocessor 19. The wiring configuration between thevariable I/O ports 18 and the peripheral hardware is prone to variationdepending upon the type of peripheral hardware (e.g. level sensor 8,pumps 10, etc.) used in the pumping station 2. The software product 20includes instructions for processor 19 to execute, and enable controller14 to perform the method 50 for determining a flow rate indicator (F)relating to the output flow rate of the activated pumps 10 of thepumping station 2. Software product 20 (including software routines) istypically provided in a memory device 17 of microprocessor 19, or on amagnetic or optical disc 21 which microprocessor 19 can access by meansof disc drive 23.

According to an embodiment of the present invention, there is providedthe method 50 performed by controller 14 and for determining a flow rateindicator (F) relating to the output flow rate of the activated pumps 10of the pumping station 2. The method 50 is described in detail belowwith reference to FIG. 3.

Initially, the method begins at step 52 when the controller 14 activatesat least one of the pumps 10 a, 10 b upon determining that correspondingactivation trigger points of the level sensor 8 have been triggered.Prior to activating the pumps 10, the controller 14 periodicallycalculates the inflow rate indicator (I) using Eq. 1 and stores thisvariable value. Upon activating the pumps 10, the controller initialisesa pump activation cycle timer to measure the duration of the presentpump activation cycle.

At step 54, the controller 14 determines an output flow rate indicator(F) using Eq. 2. The inflow rate indicator (I) used is either determinedprior to activating the pumps 10 at step 52, or updated at step 64 asdescribed in detail below. The flow rate indicator (F) is alsodetermined using the well volume rate indicator

$\frac{\Delta \; V_{well}}{\Delta \; t}$

determined by the controller 14 using measurements from the liquid levelsensor 8. The controller 14 displays the determined output flow rateindicator (F), measured inflow rate indicator (I) and measured wellvolume rate indicator on a display.

At steps 56 and 58, the controller 14 determines respective operatingconditions relating to the activated pumps 10. If either operatingcondition is satisfied, then the method 50 proceeds to step 60.Otherwise, the method 50 proceeds to step 68.

Elaborating further in relation to the operating condition of step 56,the controller 14 determines whether the pump flow rate indicator (F)determined at step 54 is less than a predetermined flow rate threshold(X). The controller 14 calculates the predetermined flow rate threshold(X) as a percentage reduction (e.g. 10%) of a prior flow rate indicator(F).

Elaborating further in relation to the operating condition of step 58,the controller 14 determines, using the pump activation cycle timer,whether the pumps have been activated for a period more than apredetermined time threshold (Y). The controller 14 calculates thepredetermined time threshold (Y) as a percentage increase (e.g. 10%) ofa prior duration that the pumps were activated in the previous pumpactivation cycle.

Responsive to the determination of one of the operating conditions atstep 56 or step 58, at step 60 the controller 14 determines whether ornot the instantaneous well liquid level measured with level sensor 8exceeds a predetermined maximum safe well level threshold (L). If themeasured liquid level in the well 4 exceeds the safe well levelthreshold (L), then the pumps remain safely activated and the method 50proceeds to step 68. Alternatively, if the measured liquid level in thewell 4 does not exceed the safe well level threshold (L), then themethod 50 proceeds to step 62.

At step 62, the controller 14 temporarily deactivates any activatedpumps 10.

At step 64, the controller 14 re-determines and updates inflow rateindicator (I) using Eq. 1. The updated inflow rate indicator (I) canlater be used when calculating the pump flow rate indicator (F) at step54.

At step 66, the controller 14 reactivates any pumps which weredeactivated in step 62.

Steps 62 to 66 typically have an introduced delay for a predeterminedperiod of time (Z) to enable enough time for an accurate inflow rateindicator (I) to be determined at step 64. The predetermined period oftime (Z) would typically be short (e.g. 10 seconds) when compared withthe pump activation cycle (e.g. of the order of minutes).

At step 68, the controller 14 determines whether the liquid level in thewell has dropped below the deactivation trigger-points along the levelsensor 8 for both pumps 10 a, 10 b. If this operating condition is notmet, the method 50 proceeds to step 54. Alternatively, if this operatingcondition is met, the method 50 proceeds to step 70 where the controller14 deactivates the pumps 10 a, 10 b and stops the pump activation cycletimer. Accordingly, the pump activation cycle has ended.

The method 50 provides for the accurate determination of the output flowrate indicator (F) of the pumps 10, by temporarily deactivating thepumps 10 during a pumping cycle to accurately measure the inflow rateand obtain the corresponding flow rate indicator (I).

A person skilled in the art will appreciate that many embodiments andvariations can be made without departing from the ambit of the presentinvention.

The preferred embodiment was described with reference to a pumpingstation 2 for emptying a sewage well as shown in FIG. 1 a. The skilledperson will readily appreciate that the present invention is similarlyapplicable to the pumping station for filling a water well as shown inFIG. 1 b. Accordingly, a method can be provided for determining a flowrate indicator (F) relating to the output flow rate of the activatedpumps 10 of the pumping station 2 shown in FIG. 1 b. That pumpingstation 2 includes a well 4 to be at least partially filled by the pumps10 and an outlet 9 through which outflow can exit from the well 4. Themethod includes the step of determining, using the controller 14, anoperating condition relating to the activated pumps 10. The methodfurther includes the step of temporarily deactivating the pumps 10 anddetermining an outflow rate indicator relating to the outflow using thepump controller 14, responsive to the determination of the operatingcondition. The method also involves determining, using the pumpcontroller 14, the flow rate indicator (F) using the determined outflowrate indicator.

The foregoing embodiments were described in relation to pumping stations2 including a pair of pumps 10 a, 10 b, although any number of pumps maybe used.

In the preferred embodiment, the volume of liquid in the well 4 wasdetermined using the liquid level sensor 8. In an alternativeembodiment, the pumping station 2 may include either a pressure sensoror an ultrasonic sensor located at the base of the well 4 to be used bythe controller 14 to determine the volume of liquid in the well 4.

In compliance with the statute, the invention has been described inlanguage more or less specific to structural or methodical features. Itis to be understood that the invention is not limited to specificfeatures shown or described since the means herein described comprisespreferred forms of putting the invention into effect. The invention is,therefore, claimed in any of its forms or modifications within theproper scope of the appended claims appropriately interpreted by thoseskilled in the art.

What is claimed is:
 1. A method executed by a pump controller fordetermining a pump output flow rate of one or more activated pumps of apumping station, the pumping station including a well configured toreceive or supply fluid flow, the method when executed by the pumpcontroller, causes the pump controller to automatically carry out stepsof: determining a pump operating condition intrinsic to the one or moreactivated pumps; temporarily deactivating the one or more activatedpumps during a pump activation cycle and determining a well flow raterelating to the fluid flow, responsive to the determination of the pumpoperating condition; and determining the pump output flow rate using thedetermined well flow rate, wherein the step of temporarily deactivatingthe one or more activated pumps involves deactivating the one or moreactivated pumps for a predetermined period of time and determining thewell flow rate over the predetermined period of time.
 2. The method asclaimed in claim 1, wherein the pump operating condition is that thepump output flow rate is less than a predetermined flow rate threshold.3. The method as claimed in claim 2, wherein the predetermined flow ratethreshold is calculated as a percentage reduction of a prior pump outputflow rate.
 4. The method as claimed in claim 1, wherein the pumpoperating condition is that the one or more activated pumps have beenactivated for a period more than a predetermined time threshold.
 5. Themethod as claimed in claim 4, wherein the predetermined time thresholdis calculated as a percentage increase of a prior duration that the oneor more activated pumps were activated.
 6. The method as claimed inclaim 1 which, prior to the step of temporarily deactivating the one ormore activated pumps, further includes the step of determining that awell level does not exceed a predetermined well level threshold.
 7. Themethod as claimed in claim 1, wherein the step of determining the wellflow rate involves using a determined well volume rate.
 8. The method asclaimed in claim 7, further including the step of displaying any one ormore of the determined: well flow rate, pump output flow rate and wellvolume rate.
 9. A method executed by a pump controller for determining apump output flow rate of one or more activated pumps of a pumpingstation, the pumping station including a well to be at least partiallyfilled by the one or more activated pumps and an outlet through whichoutflow can exit from the well, the method when executed by the pumpcontroller, causes the pump controller to automatically carry out stepsof: determining a pump operating condition intrinsic to the one or moreactivated pumps; temporarily deactivating the one or more activatedpumps during a pump activation cycle and determining the pump outputflow rate relating to the outflow, responsive to the determination ofthe pump operating condition; and determining a pump output flow rateindicator using the determined pump output flow rate, wherein the stepof temporarily deactivating the one or more activated pumps involvesdeactivating the one or more activated pumps for a predetermined periodof time and determining the pump output flow rate over that period oftime.
 10. A pump controller for determining a pump output flow rate ofone or more activated pumps, the pump controller being configured to:determine a pump operating condition intrinsic to the one or moreactivated pumps; temporarily deactivate the one or more activated pumpsduring a pump activation cycle and determine a well flow rate relatingto fluid flow of a well, responsive to the determination of the pumpoperating condition; and determine the pump output flow rate using thedetermined well flow rate, wherein temporarily deactivating the one ormore activated pumps involves deactivating the one or more activatedpumps for a predetermined period of time and determining the well flowrate over that period of time.
 11. The pump controller as claimed inclaim 10 which, prior to temporarily deactivating the one or moreactivated pumps, is further configured to determine that a well leveldoes not pass a predetermined well level threshold.
 12. A pumpcontroller for determining a pump output flow rate of one or moreactivated pumps, the pump controller including: a processor incommunication with ports for connection to the one or more activatedpumps; and a memory in communication with the processor, the memorycontaining a software product including: routines for determining a pumpoperating condition intrinsic to the one or more activated pumps;routines for temporarily deactivating the one or more activated pumpsduring a pump activation cycle and determining a well flow rate relatingto fluid flow of a well, responsive to the determination of the pumpoperating condition; and routines for determining the pump output flowrate using the determined well flow rate, wherein the routines fortemporarily deactivating the one or more activated pumps are configuredto deactivate the one or more activated pumps for a predetermined periodof time and determine the well flow rate over that period of time.